Ultra-wideband (UWB) Microstrip Bandpass Filter with Narrow Notched Band

In this paper, we introduce a compact UWB microstrip bandpass filter (BPF) with narrow notched band inside its passband. The UWB BPF is based on a circuit model for an optimum distributed highpass filter with slow wave stepped impedance connecting lines. The rejection or notched band is implemented by adding stepped-impedance resonators (SIRs). The notched band can be easily generated and set at any desired frequency and can be controlled by variety parameters. The design is successfully realized in theory and verified by full-wave EM simulation and the experiments. The obtained results are demonstrated where excellent agreement is achieved. The filter exhibits low insertion loss over the desired passbands, a sufficient attenuation level at the centre frequency of the notched band and a good out-of-band performance.